The invention relates to a percussion device having a frame, to which a tool is mountable movable in its longitudinal direction relative to the frame of the percussion device, the percussion device containing a work chamber having a transmission piston mounted movable in the axial direction of the tool to compress the tool suddenly in its longitudinal direction by the pressure of the pressure fluid acting on the transmission piston to generate a longitudinal stress pulse to the tool, which propagates through the tool to the material being crushed, inlet and outlet channels for conducting the pressure fluid to the percussion device and away from it and a control valve that has a movably mounted switch member with at least one channel so that the switch member supplies pressure fluid alternately from the inlet channel to the work chamber to act on the transmission piston, whereby the transmission piston moves in relation to the frame of the percussion device toward the tool and, correspondingly, to discharge the pressure fluid that acted on the transmission piston from the percussion device, whereby during its return movement the transmission piston moves in relation to the frame of the percussion device back to its initial position.
In the percussion device of the invention, a stress pulse is provided by arranging the pressure of pressure fluid to act on a transmission piston in a separate work chamber preferably relatively suddenly. The pressure effect pushes the transmission piston toward the tool. As a result of this, the tool is compressed, whereby a stress pulse is formed in the tool to run through the tool and, when the tool bit is in contact with rock or some other targeted hard material, to break it. In the percussion device, it is possible to use to control its percussion operation a rotating or linearly reciprocating switch member that typically has consecutive openings that alternately open a connection from a pressure fluid source to the transmission piston of the percussion device and, correspondingly, from the transmission piston to the pressure fluid container. A general problem with known solutions is the return of the piston to its initial position, which is, however, necessary to produce a continuous percussion operation. The easiest solution is to stop the transmission piston in the return direction by means of different mechanical limiters, such as shoulders. However, in solutions in which the transmission piston could rotate around its axis, this would cause friction and wear. Another problem is that when the transmission piston contacts the limiter, it is possible that material deformation and breakage result in the long run.